Roof reflector for a high temperature small reactor

ABSTRACT

A graphite roof reflector for a small, high temperature reactor is arranged under the hot gas collector space and is therefore exposed to high thermal and radiation loads. In order to make possible the satisfactory support over the entire operating life of the reactor, the roof reflector is assembled from a center part and an annular part, which are supported in a different manner. The annular part is supported on the side reflector of the reactor. The center part is suspended by means of tie rods from a cover located over the hot gas collector space. The tie rods are placed into bores of the cover through which cold gas flows.

This application is a continuation of application Ser. No. 553,034 filedNov. 18, 1983, now abandoned.

BACKGROUND OF THE INVENTION Field of the Invention

The invention concerns a roof reflector for a small high temperaturereactor having a reactor core, a cold gas collector space, and a hot gascollector space. The reactor arrangement also includes a cover for thereactor core separating the core from the cold gas collector space, anda side reflector surrounding the reactor core. The roof reflectorconsists of an outer and an inner ring arranged over the cover and topparts of the side reflector.

BACKGROUND OF THE INVENTION

In small sized high temperature nuclear reactors of this type, thelayout of the roof reflector is the cause of design problems due to theexposure of the reflector to high temperatures and to radiation. Afreely projecting roof is not possible because of the great span width.A suspension of the roof reflector, for example by means of metalfastening elements, is not feasible because of the fact that suchfastening elements would have to be replaced under certain conditionsseveral times during the 40-year operating life of the nuclear powerstation which would be highly disadvantageous.

SUMMARY OF THE INVENTION

It is an object of the invention to provide with simple means a roofreflector of the aforementioned type with a satisfactory support withoutthe need to replace the fastening elements.

This object is achieved according to the invention by a roof reflectorcomprising a center part and an annular part surrounding the centerpart. The annular part is supported on the outer ring of the sidereflector and the center part is suspended from the reactor core coverby means of fastening elements. The fastening elements are cooled overtheir entire length with cold gas from the center part of the cover.

In a preferred embodiment, a plurality of tie rods are provided for thefastening of the center part of the roof reflector. The tie rods arearranged in bore holes present in the center part of the reactor cover.The bores are in communication both with the cold gas collector spaceand the hot gas collector space. As the result of the higher pressure ofthe cold gas with respect to the hot gas, the tie rods are constantlyexposed to a flow of cold gas. The bores are dimensioned so that in thecase of a minimum flow of cold gas to the hot gas collector space andadequate cooling of the tie rods, overall efficiency is affected onlynegligibly.

The divided configuration and the means to fasten the roof reflectoreliminate the aforementioned layout problems and render the securemounting of the roof reflector possible without the requirement ofreplacing fastening elements over the entire operating life of thereactor.

BRIEF DESCRIPTION OF THE DRAWING

An example of an embodiment of the invention is described hereinbelowwith reference to the drawing attached hereto.

In the drawing:

FIG. 1 shows the lower and intermediate area of a nuclear power stationwith a small, high temperature reactor;

FIG. 2 shows the intermediate area of the nuclear power station with theroof reflector in an enlarged sectional view.

DETAILED DESCRIPTION OF EMBODIMENTS

As shown in FIG. 1, the reactor core 10 is located in the lower area ofthe nuclear power station. The core is enclosed by the reactor pressurevessel and surrounded by a floor reflector 14, a side reflector 16consisting of two rings together with the thermal side shield 18 rigidlyconnected with it, and a roof reflector 50. In the upper area over thereactor core 10, several steam generators 22 are arranged. The steamgenerators are exposed to hot gas from below. Blowers, which are notshown in the drawings, are installed above the steam generators 22. Acold gas collector space 24 is located between the steam generators 22surrounding them.

Above the roof reflector 50 a graphite cover 26 partially defining a hotgas collector space 28 is arranged. The graphite cover 26 separates thehot gas collector space 28 from the cold gas collector space 24. Thecover 26 is fixedly connected in the radial direction with the thermalside shield 18.

The roof reflector, designated in its entirety by 50, consists of acenter part 51 and a multilayer annular part 52 arranged concentricallyaround the center part 51 (FIG. 2). The annular part 52 is supported onthe outer ring of the side reflector 16 and is fastened radially to thethermal side shield 18. The center part 51, on the other hand, issuspended by means of tie rods 54 from the center part 56 of thegraphite cover 26, wherein the tie rods 54 are arranged in longitudinalbores 58 of the cover 26, through which cold gas is flowing. Thelongitudinal bores 58 are connected with the hot gas collector space 60by means of transverse bores 60.

Due to the pressure of the cold gas being higher than that of the hotgas, cold gas flows around the tie rods 54 and they are cooledadequately. The cold bores 58 are dimensioned so that with a minimumflow of cold gas and with sufficient cooling the overall efficiency ofthe reactor is affected only negligibly.

The above description describes a preferred embodiment of the invention.It is to be understood however, that the invention is not limited to anysingle embodiemnt or feature, but should be construed to cover allmodifications and alternative embodiments falling within the scope ofthe invention as defined by the claims which follow.

What is claimed is:
 1. A small gas cooled high temperature reactorhaving a reactor core, cooling gas, a cold gas collector space and a hotgas collector space above said reactor core, a cover separating saidcold gas collector space from said hot gas collector space, a sidereflector surrounding said reactor core and formed of an outer ring andan inner ring, a roof reflector between said reactor core and said hotand cold gas collector spaces, said roof reflector further comprising:anannular part supported on the outer ring of the side reflector, a centerpart surrounded by said annular part, means for suspending said centerpart from said cover, and means for diverting said cooling gas forcooling said means for suspending comprising cooling gas conduits,wherein said annular part and said center part are graphite.
 2. A smallhigh temperature reactor as in claim 1, wherein said cooling gasconduits comprise bores provided in the center part of a cover connectedwith both the cold gas collector space and the hot gas collector spaceand said means for suspending comprises tie rods arranged in said bores.3. A small high temperature reactor as in claim 2, wherein the bores aredimensioned to restrict flow of cooling gas from said cold gas collectorspace to said hot gas collector space to only sufficiently cool said tierods.
 4. A small high temperature reactor having a reactor core, a coldgas collector space and a hot gas collector space above said reactorcore, a cover separating said cold gas collector space from said hot gascollector space, a side reflector surrounding said reactor core andformed of an outer ring and an inner ring, a roof reflector between saidreactor core and said hot and cold gas collector spaces, said roofreflector further comprising:an annular part supported on the outer ringof the side reflector, a center part surrounded by said annular part,means for suspending said center part from said cover, means for coolingsaid means for suspending comprising cooling gas conduits, wherein saidannular part and said center part are graphite, and wherein said coolinggas conduits comprise bores provided in a center part of the coverconnected with both the cold gas collector space and the hot gascollector space and said means for suspending comprises tie rodsarranged in said bores.
 5. A small high temperature reactor as in claim4, wherein the bores are dimensioned to restrict flow of cooling gasfrom said cold gas collector space to said hot gas collector space tosufficiently cool said tie rods.